The present invention relates to a grazing incidence reflection spectrometer which operates to direct light obliquely onto a sample surface and detects the light which is reflected therefrom, whereby the electronic absorption spectrum of a chemical species at the sample surface is measured with a high sensitivity.
With the development of fine dry processing in the production of a semiconductor device etc., it is required to exactly determine a reaction mechanism at a solid-gas interface. Therefore, several studies have been made on methods and apparatuses for non-destructively observing an adsorption phenomenon which is the initial process of the surface reaction.
Among them, a method of measurement with the traveling direction of incident light set at an angle at which it is nearly parallel to a sample surface has already been employed for total reflection and Bragg reflection measurements in the X-ray region as stated in, for example, an article by T. Kawamura and T. Fukamachi (`Journal of the Spectroscopical Society of Japan`, Vol. 31, No. 4, 1982, pp. 269-281). According to this method, it is possible to obtain information on a crystal structure in the vicinity of the sample surface and the structure and the nature of bonding of a layered adsorption film at the sample surface. With such measurement method, however, it is difficult to obtain detailed knowledge on the electronic structure of a chemical species which is adsorbed to the sample surface in a non-layered fashion.
Here, unless otherwise specified, the "sample" shall indicate a substrate which includes a smooth surface having no chemical species adsorbed thereto, and the "chemical species adsorbed to the sample surface" shall signify a chemical species which has an interaction with the sample surface including ordinary physical adsorption or chemical adsorption (the same applies hereinbelow).
In addition, a measurement method wherein linearly polarized light whose plane containing the electric vector and the direction of propagation (referred to as the "plane of polarization" henceforth) is parallel to a plane of incidence is used as incident light and an angle defined between the incident light and the sample surface is set at about 20.degree. to 30.degree. so as to enlarge the amplitude of electric field vibration at the sample surface, has been employed for the reflection spectrometry of the adsorbed molecular species of a metallic sample surface in the infrared region (by W. Suetaka in `Journal of the Spectroscopical Society of Japan`, Vol. 31, No. 3, 1982, pp. 195-210). According to this measurement method, knowledge on the nature of the bonding between the adsorbed molecular species and the sample is obtained from the vibrational spectrum of the adsorbed molecular species. With only this measurement method, however, it is difficult to obtain detailed information on the electronic structure as concerns the mechanism of the surface reaction of the sample. Moreover, this measurement method is restricted to the case where the sample is metal, and it is also subject to the limit in application that the adsorbed species must be a molecule.